1. Field of the Invention
The present invention relates to a manifold reactor mounted in an internal combustion engine for purifying exhaust gases and, more particularly, a seal structure for connecting portions of the outer and inner cores at an exhaust gas inlet port in a multi-walled manifold reactor including the outer and inner cores.
2. Description of the Prior Art
The manifold reactor is a device for purifying exhaust gases from an internal combustion engine by recombusting harmful unburned components such as HC and CO contained in the exhaust gases by utilizing the heat owned by the exhaust gases themselves thereby effecting high temperature oxidization in a reactor chamber. Since the reactor chamber is provided directly adjacent the exhaust ports of the engine thus eliminating the conventional exhaust manifold so as to maintain the temperature in the reactor chamber as high as possible.
Manifold reactors are generally designed as a dual or tripple walled structure including an outer core, inner core or the like in order to provide better heat insulation for the reactor chamber so that the high temperature oxidization to take place in the reactor chamber is effected more efficiently and to provide a sufficiently long dwell time for the exhaust gases in the reactor chamber to accomplish required recombustion thereof. In conventional manifold reactors of this type, the space defined between the inner and outer cores are generally filled with a solid heat insulating material such as glass wool or the like. In this type of manifold reactor, the outer core generally has an inlet tube mounted at its exhaust gas inlet portion while the inner core has a tubular portion for introducing exhaust gases therein, said inlet tube and said tubular portion being telescoped with each other to form a connecting portion which communicates with inlet port defined by said inlet tube to the interior of the combustion chamber defined by the inner core. In this case, the telescoping connecting portions must be loosely engaged with each other so as to allow for different radial thermal expansion of said inlet tube and said tubular introductory portion of the inner core. A clearance required for this release of different thermal expansion requires a radially yieldable seal structure because, otherwise, chips or flocks of the solid heat insulating material filling the heat insulating intermediate space will enter into the reactor chamber or the exhaust system, thus causing a danger of possibly damaging a catalytic converter.
Conventionally, the seal structure employed in this connecting portion comprises a metal flange element mounted around the downstream end of the inlet tube. A similar metal flange element is mounted around the upstream end of the tubular inlet portion of the inner core. Said latter flange element being attached with an annular element having an L-shaped cross section by welding or similar joining means thereby providing an annular channel provided at the leading end of said tubular inlet portion of the inner core so that the annular flange element mounted at the downstream end of the inlet tube is received in an annular channel provided by said annular channel member in a manner such that it is sandwiched between said second mentioned annular flange element and said annular member of L-shaped cross section, thus allowing for a relative displacement of the engaging members in the radial directions.
However, in this conventional sealing structure, since the sealing performance is obtained by the contact of metal flange surfaces, a relatively high accuracy working and assembly are required in order to obtain a desired sealing performance. Furthermore, since these sealing portions are subject to relatively severe thermal expansion and contraction in succession as well as high temperature errosion, even when the seal structure has been manufactured in a sufficiently high accuracy to provide a desired sealing performance in an initial stage of operation, the sealing performance is not maintained for a long period during operation, thus rapidly deteriorating the sealing performance. If the sealing performance lowers, chips and flocks of the solid heat insulating material traverses through the sealing portion toward the inside of the inner core due to the vacuum generated at the exhaust gas inlet portion of the manifold reactor caused by pulsating flow of exhaust gases, thus chips and flocks enter the engine cylinders with the result that piston rings are rapidly worn and, at worst, the engine is broken.